Comments on: Teaching the Math of Climate Sciencehttps://johncarlosbaez.wordpress.com/2012/12/18/teaching-the-math-of-climate-science/
Sat, 10 Dec 2016 00:33:28 +0000hourly1http://wordpress.com/By: Nathan Urbanhttps://johncarlosbaez.wordpress.com/2012/12/18/teaching-the-math-of-climate-science/#comment-23153
Wed, 19 Dec 2012 16:58:52 +0000http://johncarlosbaez.wordpress.com/?p=13469#comment-23153It’s not really feasible to build a web interface to run a modern AOGCM with perturbed parameters. Or rather, you could build the interface, but you wouldn’t get results within any reasonable time frame. CESM takes over 2 real-time days to simulate 100 years of climate … using 2000 cores on a Cray XT5 supercomputer. And if you perturb parameters, you may have to spin the model up for more than 100 years just to get to a self-consistent and physically reasonable quasi-steady state (especially if you perturb something outside of the atmosphere, which has faster response times). If you stick to small perturbations of atmospheric parameters, maybe you could cut this time by 10, but you’re still talking about hours of computing time on thousands of cores. You could also lower the resolution (e.g. closer to EdGCM), but I still don’t see this being feasible.

Even with a model as simple as EdGCM, I don’t think this is very feasible … you’re certainly not going to get results very quickly, although I haven’t kept up with its performance on multicore systems. (Last time I used it, it wasn’t multicore-aware.) Anyway, I think it’s a benefit, not a limitation, that EdGCM has fewer perturbable parameters than a modern AOGCM. Users aren’t going to know what to do with hundreds of esoteric parameters.

Perhaps more feasible would be a web interface to browse the output of the existing Climateprediction.net perturbed physics ensembles. These were generated by distributing parts of AOGCM simulations to users’ PCs and waiting the necessary weeks or months for outputs to be produced.

]]>By: Erichttps://johncarlosbaez.wordpress.com/2012/12/18/teaching-the-math-of-climate-science/#comment-23128
Wed, 19 Dec 2012 00:16:00 +0000http://johncarlosbaez.wordpress.com/?p=13469#comment-23128Many GCMs are essentially open-source these days. CESM and all of its predecessors have been publicly available and community-built. You can now download the source code for the GISS model (the one upon which EdGCM is based) and the GFDL model. Of course they are not simple to compile and run. There is nobody who will get paid to turn these models into “apps” that would be simple to install and run. What would be nice is a web interface to set the parameters and run one of these models. Conceivably, this could be done in such a way that it could either control a local installation of the model or a remote installation hosted somewhere else. This is somewhat akin to what EdGCM is, but the number of parameters that you can change with EdGCM is very limited.

Herein lies the challenge: The real power of GCMs is to test the sensitivity of the model solution to different boundary conditions or internal physical parameters. There are so many interesting possibilities, that it is difficult to conceive of an interface that students could become familiar enough to use in a short period of time that would also allow them to unlock all of this potential.